The present invention relates to a plate-type heat exchanger for use in heaters, air conditioners, or the like, and more particularly to a core plate for defining a fluid tube pass in such a plate-type heat exchanger.
Conventional plate-type heat exchangers include a stack of fluid pass tubes each composed of a pair of core plates having edges joined together and formed with rows of ribs across the tube pass so as to provide fluid paths shaped for increased heat transfer efficiency. According to one known design, however, the ribs are formed in aligned rows between the fluid inlet and outlet of the fluid pass so that linear flow paths free of ribs are defined between the inlet and the outlet. Since the fluid tends to flow through such linear fluid paths from the inlet to the outlet, the heat transfer efficiency is poor. In addition, the core plates are mechanically weak along the linear flow paths between the rib rows. Another prior heat exchanger fluid tube pass, designed to overcome the problems of the aforesaid conventional fluid tube pass, is disclosed in U.S. Pat. No. 4,470,455 issued Sept. 11, 1984 to Sacca. The patented heat exchanger fluid flow pass does not have rib-free fluid passages extending longitudinally between the inlet and the outlet, but imposes increased resistance to the fluid flow from the inlet to the outlet, resulting in greater pressure loss. Another difficulty with this fluid flow pass is that it is mechanically weak along transverse rib-free lines across the fluid flow pass.